Pharmacokinetics of Antiretroviral Drugs in Lactating Women and Breastmilk Fed Infants Under 6 Months of Age in Botswana

Inclusion Criteria Mothers/Infants: 1. Lactating women ≥18 years of age who are receiving at least one DOI per SOC who are ≤180 days postpartum, and their infants (≤180 days of age) who receive maternal breastmilk. 2. Informed consent, according to local IRB/REB/IEC guidelines, prior to any study-related procedures. 3. If the mother is receiving more than one DOI, the mother must have taken all DOIs that she is receiving concomitantly for the 6 doses prior to sample collection. 4. Mother participant is fluent in English or Setswana. 5. Willing to provide at least 1 of the below required samples between the co-enrolled mother/infant pair: * Maternal breastmilk * Infant blood Exclusion Criteria Mothers/Infants: 1. Any concomitant condition which, in the opinion of the participant's healthcare provider, the site principal investigator (PI), a research nurse, or designee conducting the study, would preclude participation in the study. 2. Known pregnancy of mother during sample collection. 3. Mother has pumped any breastmilk at all in between the last 6 direct infant feedings prior to sample collection. 4. Infant was fed breastmilk in any manner besides nursing at mother's breast for any of the last 6 feedings prior to sample collection. 5. Previous enrollment on this study.